This invention arises in the sheet metal forming context. Sheet metal flashing utilized for sealing and finishing roof edges is produced in the form of custom formed elongated sheets of varying length. In use the sheets are customarily interlocked at their ends by means of a conventional slip lock joint. This joint is effected by forming in one end of the sheet a slip lock which is essentially in the form of a flattened "S". The unformed end of an adjacent sheet is simply slid into the fold presented by the slip lock.
This slip lock must be formed on substantially every piece of flashing used in the roofing industry. As presently practiced the formation of the slip lock is a very labour intensive and therefore expensive procedure. There is therefore a need for a means of forming a slip lock in a more efficient manner than that presently utilized. It is against this background that the present invention arises.